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solar panel current problem

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electrominds

New Member
i connected 2 solar panel of 130 watts in parellel. single solar panel should give 8.2 ampere so connected parellel that must give atleast 16 ampere. but it gie only 7.9 ampere ie 4.2 amp & 4.5 amp from ist and 2nd cell if measure individually. also when i connect load i.e 145 AH battery very close to parellel connected solars then all thing alright give 16 amp. is it line or distance or cable loss? if yes then how can i solve my problem
 
try using high current carrying wires to connect it to the battery....probably ur wires are not able to carry the current....
check if the wires are gettin heated..if they are,use thicker wires that can carry atleast 20amp...this should solve your problem
 

Tedfred

New Member
Ok here is how it works. The ohms law in simple states that the panels delivers voltage, and the battery draws current off of the panels. So you need to look at the battery for the answer. For the monument we will replace the battery with a big adjustable resister. Start with a high resistance and very little current will be drawn off of the panels. Lower the resistance and the current increases until you get 16 amps and as you stated you will get 16 amps. Or there about for the two panels. Now place a volt meter across the panels and you will find maybe 10 volt or 11 maybe 12 but not likely more then 12 volts. Now back to the battery. A fully charged battery requires 13.8 volt or more before it starts drawing current off the panels. To get the battery to pull off 16 amps of current the volt will have to be in around 14.5 volts This is just the way batteries work. If run the battery clear down you will find that you will have a good 16 amps of current for a short time. And the battery will only have a small charge on it. and then back to the 4 amps or so. To fix this dilemma you will have to add a few more cells to each panel to increase the voltage from the 12 or so volts to 14 volts or so. There are special inverter to handle this job but they are not cheep.
 

chemelec

Well-Known Member
Post #3 is Correct.

Post #6 is Probably Not.
Most Solar panals Made for charging 12 volt Batteries have an Open Voltage of around 17 to 18 Volts.
Tis is more than enough voltage to charge at Full Current.
Assuming you have Enough Sunlight.

"Like the Sahara Desert, 12 Noon, Hottest Day Ever and with the Panal at 90 Degrees to the Sun".

But on Some panals, rated current is at a DEAD SHORT, also assuming the above conditions.
 

tsveti

New Member
Hello "electrominds", did you solve the problem with the solar panel current?
I am interested in solar panels as well. I am going to build small solar system for 12V.
As you know we first have to charge the 12V battery and then to convert the 12V DC voltage to 220V AC voltage using an inverter.
Charging the battery is not so easy. You have to build charging controller. The normal voltage of the solar panel is about 17V and the open circuit volage is about 21V.
The solar panel has VA characteristics for various irradiances. There is maximum power line crossing these characteristics. In order to guarantee maximum efficiency of the solar panel, the charging controller must keep the panel work always on the Max Power Line.
 

mneary

New Member
Maximum power point is a nice to have, but it's easy to waste more than you gain.

If you simply use your 17V solar array as a 'constant current' through a diode into a "12V" battery with an actual terminal voltage of 13.8V, you've wasted at the most (17-14)/(17) or 18% of the solar power.

Sure, it's possible to design a MPPT controller that's 82% efficient, and for truly large arrays the investment is economically justified.
 

RCinFLA

Well-Known Member
It might be wire loss but more then likely when you measured the two in parallel you let the voltage get too high. From what you said sounds like 32 cells in series on each panel. (usually there is 36 cells for a 12v application).

Each cell is an illumination based current source with a parallel shunt diode.

Unloaded all the generated current goes down the inherent diode. Depending on panel temp the forward drop is about 0.6 vdc per cell.

To get max power you want to load the cell to point where just a little of the generated illumination current goes down the inherent diode. This is about 0.5vdc per cell at 25 deg C.

The generated current will stay relatively flat as voltage is reduced by load. This is why you got the right current when battery brought voltage down.
 
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Oznog

Active Member
Actually the rating's not for "Sahara at noon".
It's for 1Kw/m^2 at 25C with the panel facing the sun.

You can look up the insolence for your city, they even have annual insolence averages which accounts for latitude, hours of sunlight per day, average cloud cover and dust, and seasons.

Sunlight at southern latitudes, on clear days, can exceed 1Kw/m^2 easy.
However, there are many factors to degrade the output:
The sun being reduced early and late in the day
The sun being reduced in seasons other than summer
Cloud cover, or dust in the air
The angle of a fixed panel not adjusted for seasons
The angle of the panel not tracking the sun
The glare off of the clear panel material covering the cells
The panel being dirty
The panel being >25C. This is quite significant, and few panels make any meaningful provisions for cooling the cells in the sun.
Panel degradation (can be 10%-15% in a few yrs exposure to sun after mfg).
 
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ama23

New Member
If you really want to increase the productivity u can put a matrix of white led on each panel. This will ensure creating power during day and night. You also can take the power for these leds from the Solar panel i.e. closed cycle.
 

Mr RB

Well-Known Member
If you really want to increase the productivity u can put a matrix of white led on each panel. This will ensure creating power during day and night. You also can take the power for these leds from the Solar panel i.e. closed cycle.

Yep that's the best way to do it alright. :D
 

russpatterson

New Member
If you really want to increase the productivity u can put a matrix of white led on each panel. This will ensure creating power during day and night. You also can take the power for these leds from the Solar panel i.e. closed cycle.

Am I missing something? Is this meant to be sarcastic? Is the suggestion to power the panel with LED's run from the panel so you get power day and night?

From back in this thread when things were making sense: The way I understand panel characteristics and the value of MPPT voltage transformations is that the panel has a maximum current (the open circuit current you can test by measuring amps with your meter and connecting both panel leads). As the voltage gets pulled down, due to load, low battery, etc. then you reach a point where the maximum current is reached and you start losing power (watts output) as the voltage goes down since watts = voltage x current.

So the idea is to do a DC/DC conversion using a switching converter so that the panel side sees the high voltage and the load side sees the lower voltage but with a higher resulting current. This way you don't lose those watts when the load is pulling the voltage down.

Try connecting your panels directly to your multimeter (in current mode) and see how much they put out. Then try the same test near your battery (over the wires in question) without the battery or load connected, to see if the guage of your wiring is the issue.
 

colin55

Well-Known Member
To solve your problem you can do one of the following:
1. Increase the size of the cables between panel and battery or move the battery closer.
2. Add a small 2v panel in series with each panel. This will be 4 series-cells with the capability of 8 amps. For example, if each cell is capable of 500mA, you will need 16 x 4 cells.
3. Add a DC-DC inverter that will increase the line voltage by about 2v. This will take the 12v and draw 2amps to produce 2v at 8 amps.
 

Superman--

New Member
Have you used a diode so you don't get feed back between the cells so they don't effect each others hertz?
After that try connecting it to a battery.
This worked for me on my boat because the motor doesn't have a alternator and I went to solar to charge it.
And when I combined the two on the battery I didn't get the proper load amperage from the cells when I turned on the bilge pump.
It turned out to be the frequency of the DC motor and the cells that made it turn into a resistor rather than a charger.
 
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